1. Field of the Invention
The present invention relates to a sheet processing apparatus for performing post-processing, such as stapling processing performed by a stapler, on sheets processed e.g. by an image forming apparatus, and the image forming apparatus including the sheet processing apparatus.
2. Description of the Related Art
There has been known a sheet processing apparatus connected to an image forming apparatus to perform post-processing, such as stapling processing (binding processing) performed by a stapler, on sheets conveyed from the image forming apparatus. More specifically, in the sheet processing apparatus, a sheet bundle is formed on an intermediate tray, and a stapler staples the trailing end of the sheet bundle using metal staples, whereby the sheet bundle is bound. After having been bound, the sheet bundle is conveyed along a conveying path provided on the intermediate tray, and is then discharged onto a discharge tray for sorting. In this case, a staple detection sensor is provided on the conveying path so as to detect the presence or absence of the staples during conveyance of the sheet bundle, whereby it is determined whether or not the sheet bundle has been normally bound. If the sheet bundle has not been normally bound, stapling processing is performed again on the sheet bundle using a saddle-stitching stapler provided downstream of the conveying path, and then the sheet bundle is discharged onto the sorting discharge tray in a positively bound state (see Japanese Patent Laid-Open Publication No. 2005-263441).
However, to detect staples used for binding processing at a plurality of points on a sheet bundle are detected on the conveying path, it is required to provide staple detection sensors corresponding in number to the staple points, which causes an increase in manufacturing costs of the apparatus. Further, to detect the staples by a smaller number of sensors, it is required to employ a method of performing detection while shifting the sensors, for example. With such a configuration, it is required to newly provide a drive mechanism for shifting the sensors, which also causes an increase in manufacturing costs of the apparatus.